With the escalation of fuel and electricity costs in recent times, there has been increased interest in using wind turbines to drive reciprocating downhole pumps.
In the design of such systems, an important component is the coupling mechanism, which connects the rotating output shaft of the tower-mounted wind turbine with the load rod.
This coupling mechanism must, of course, convert the rotating output of the turbine shaft to a reciprocating output which can drive the load rod.
As the output power of the wind turbine varies with variations in the wind velocity, the coupling mechanism should also therefore incorporate a means for varying the pump load to match it with the wind turbine output to maintain a desired system efficiency, normally the maximum achievable efficiency. As the hydraulic head of the pump load remains substantially constant, such means for varying the pump load must therefore work by changing the length of the reciprocating stroke of the load rod.
The present invention is concerned with providing a coupling mechanism which has such capabilities, namely: the capability to convert rotating output to reciprocating output; and the capability to match the pump load with the wind turbine output by varying the stroke length.
In connection with such a coupling mechanism, it is desirable that it be characterized by some or all of the following:
(1) that the mechanism be adapted to automatically vary the stroke length in such a manner as to maintain the wind turbine operating at about its maximum efficiency over a range of wind speeds;
(2) that the mechanism be "self-powered", so there is no need for electric power or a fuel-powered engine; and
(3) that the mechanism be reasonably simple, to reduce difficulties in maintaining it.